linux-kernel - Re: [RFC PATCH 10/10] vfio/type1: Register device notifier

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Message-ID: <20210225195440.GG250483@xz-x1>
Date:   Thu, 25 Feb 2021 14:54:40 -0500
From:   Peter Xu <peterx@...hat.com>
To:     Jason Gunthorpe <jgg@...dia.com>
Cc:     Alex Williamson <alex.williamson@...hat.com>, cohuck@...hat.com,
        kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH 10/10] vfio/type1: Register device notifier

On Thu, Feb 25, 2021 at 03:17:14PM -0400, Jason Gunthorpe wrote:
> It is a use-after-free. Once the PFN is programmed into the IOMMU it
> becomes completely divorced from the VMA. Remember there is no
> pin_user_page here, so the PFN has no reference count.
> 
> If the owner of the VMA decided to zap it or otherwise then the IOMMU
> access keeps going - but now the owner thinks the PFN is free'd and
> nobody is referencing it. Goes bad.

Sounds reasonable.  Thanks,

-- 
Peter Xu